1. Field of the Invention
The present invention relates to an apparatus for controlling addresses of symbol data for correcting errors of digital data, and more particularly, to an apparatus for controlling addresses of symbol data for correcting errors in a digital versatile disc (DVD) system.
2. Description of the Related Art
In a DVD system, data recorded in a disk is read during reproduction and an error correction of a Reed-Solomon (RS) product code type is performed. At this time, the read data is aligned in a virtual two dimensional state. The error corrections are respectively performed in the directions of horizontal and vertical axes. Accordingly, a two dimensional error correction effect is obtained. FIG. 1 shows structures of a data sector 10 and of an error correcting code (ECC) block 12 for the error correction in the DVD system. The data recorded on a disk (not shown) is read by a series of one-bit data columns. A bit stream in units of 16 bits is demodulated in a symbol data pattern of eight bits in a demodulating circuit (not shown). The error corrections with respect to the symbol data are respectively performed in the horizontal and vertical directions in the virtually arranged ECC block 12.
The ECC block 12 of the symbol data for the error correction is formed of 172 bytes.times.12 rows.times.16 data sectors excluding a parity and is comprised of pure symbol data forming 172 bytes.times.192 rows including the 16 frame rows of the data sector. A data structure of 182 bytes.times.192 rows is formed by adding an inner parity (PI) of 10 bytes for the error correction of the symbol data. The entire data of 182 bytes.times.208 rows to which an outer parity PO of 16 bytes is added to each of 182 columns is modulated and is recorded on a disk.
Here, when the respective symbol data are B.sub.i,j (i=0 through 207, j=0 through 181), a surplus polynomial R.sub.j (X) comprising 172 columns including outer parity is shown in the following Equation (1). ##EQU1##
wherein, ##EQU2## PA1 wherein, ##EQU4## PA1 and .alpha. represents a primitive root of a primitive polynomial. Here, the positions of the respective symbol data other than the values of the respective symbol data are included in the components to be error corrected. Namely, the symbol data demodulated from the bit stream read from the disk must be recorded on a virtual original position in the ECC block 12 of FIG. 1. Accordingly, it is possible to detect and correct the data having errors during the error correction. When the symbol data demodulated from the bit stream is recorded one byte later or one byte earlier, and thus not recorded on the row to be recorded, a large number of error are generated. Accordingly, the error correction is not possible.
Also, the surplus Polynomial R.sub.j (X) comprising the 208 rows including inner parity is shown in the following Equation (2). ##EQU3##
In the DVD system, a data unit of 91 bytes shown in the sector 10 of FIG. 1 is defined as even and odd frames in order to process various data. The respective frames are divided by frame syncs. The structures of the frame syncs are shown in FIG. 3A. The respective frames are earlier, thus forming the sector 10 of FIG. 1. The ECC block 12 which is a basic unit of the error correction is comprised of the sectors. Accordingly, a proper error correction is performed.
Therefore, when the symbol data is stored for the error correction, an apparatus for controlling addresses is required by which it is possible to improve the efficiency of the error correction by storing the symbol data in the memory so that the positions of the respective symbol data precisely correspond to the alignment of the symbol data of the ECC block.